1. Field of the Invention
This invention relates to a lubricating oil supplying device for supplying a lubricating oil to a 2-cycle engine, etc.
2. Description of the Background Art
An oil pump is conventionally used as a device for supplying lubricating oil to a 2-cycle engine. In the conventional oil pump, a plunger, formed with a pump chamber therein, is arranged within a cylinder such that the plunger can be freely rotated and reciprocated. An inlet port and an outlet port communicate with the pump chamber formed by the plunger in the cylinder. A wheel is formed on an outer circumferential surface of the plunger. The plunger is rotated by engaging this wheel with a driving worm operated by the engine. Thus, the pump chamber of the plunger is intermittently communicated with the inlet port and the outlet port formed in the cylinder. A cam is arranged at one end of the plunger and is biased by a spring so as to come in contact with a cam shaft. The stroke length of axial movement of the plunger is adjusted by rotation of the cam shaft.
In the above-described oil pump, pump action is achieved by changing the volume of the pump chamber formed in the plunger by the rotating and reciprocating movements of the plunger. Thus, the oil is discharged from the outlet port via the inlet port and the pump chamber, and is supplied to the engine.
The amount of discharge of the oil is related to the stroke length of the reciprocating movement of the plunger. This stroke length of the plunger is controlled by the shape of the cam shaft. The cam shaft coming in contact with the cam of the plunger is conventionally designed so that the amount of oil discharge is changed in accordance with the degree of opening of the throttle valve of a carburetor.
However, in the conventional design for controlling the amount of oil discharge in accordance with the degree of opening of the throttle valve of the carburetor, the amount of oil required for a given operating situation cannot necessarily be supplied to the engine at any time. For example, Japanese published (Kokoku) Patent No. 7-65489 is proposed as a solution to this problem. In this prior art, two inlet ports and two outlet ports are arranged to communicate with the pump chamber, and a spool valve for adjusting the amount of oil discharge is operated by a solenoid and is arranged in a discharge passage connected with the outlet ports. Operation of the solenoid is controlled in accordance with the operating state of the engine so that an appropriate amount of oil is supplied to the engine.
An increase in the number of outlet ports of the oil pump is one approach to provision of more appropriate control of the amount of oil supply to the engine. However, this approach encounters a problem in that it is difficult to increase the number of outlet ports for communicating the pump chamber within the plunger and the outlet ports with each other as in the conventional structure.
Further, the conventional oil pumps encounter a problem in that they are positioned where they are severely vibrated, and the amount of oil discharge cannot be appropriately controlled due to this vibration.
Furthermore, the oil pumps used in snowmobiles encounter the problem that the oil viscosity, due to low ambient temperatures, is so high that a delay is encountered in establishing the appropriate amount of discharge after the oil pump is started.
In consideration of the above points, an object of the present invention is to provide a lubricating oil supply device in which the amount of oil discharge can be finely controlled by provision of many outlet ports, and the appropriate amount of oil discharge can be secured by reducing influences of vibration.
Another object of the present invention is to provide a lubricating oil supplying device for rapidly returning the oil discharge amount to an appropriate level after the lubricating oil supplying device is started in low temperatures.
To achieve the above objects, the present invention provides a lubricating oil supply device which comprises a pump for discharging oil introduced from an oil tank, and a spool valve unit including open-close valve means having a spool valve and a solenoid for controlling operation of the spool valve. The open-close valve means is provided with plural inlet passages for introducing the oil from said pump, and an outlet passage having one end in communication with the inlet passages and the other end in communication with an engine. A return passage serves to return the oil of the open-close valve means to the pump. A communication hole in the valve spool provides communication between the inlet passages and the return passage. When the solenoid is turned xe2x80x9cOFFxe2x80x9d, the communication of the inlet passages and the return passage is interrupted by the valve spool, and the oil is discharged from the pump to the engine via the inlet and outlet passages. When the solenoid is turned xe2x80x9cONxe2x80x9d, the inlet passages are brought into communication with the return passage via the communication hole through the valve spool, and the oil discharged from the pump to the inlet passages is returned from the communication hole to the pump via the return passage.
Further, in the present invention, an introducing passage in communication with the oil tank at one end and in communication with the return passage at the other end is formed within the solenoid, and the oil from the oil tank passes through the introducing passage within said solenoid.